You can find some postings on these topics at our blog, www. Previous Next. Using Fourier transforms, Chang improved on classic FDM technology by making the sub-channels overlap: In , Saltzberg analyzed and demonstrated the performance of efficient parallel data transmission systems. This cyclic extension converts the linear convolutive channel to simulate a channel performing cyclic convolution, thus ensuring orthogonality over a time dispersive channel and eliminating ISI completely between subcarriers as long as the cyclic extension remains longer than the impulse response of the channel: As shown in the figure above, the length of T G is long enough to absorb the tail of the delayed copy signal.
Justin Barnes, Hazem H. Related Posts. Toggle Sliding Bar Area. Reach us by phone or fax Phone worldwide : Phone toll free in North America : Fax: 1 This can be an issue in some circumstances even with the much lower data rates that are transmitted in the multicarrier OFDM signal. The basic concept behind the OFDM cyclic prefix is quite straightforward.
The cyclic prefix performs two main functions. The cyclic prefix is created so that each OFDM symbol is preceded by a copy of the end part of that same symbol. Different OFDM cyclic prefix lengths are available in various systems. Otherwise, we suffer from inter-symbol interference, which cannot be represented by the circular convolution on the FFT window.
Hence, we can write the expression for the received signal within the FFT window also with a circular convolution:. It's only this property of OFDM which allows to perform the one-tap equalization with the channel impulse response. The convolution theorem in discrete domain states. Then, we can perform the simple equalization. It's exactly this propertly of OFDM which made it so popular for being used in multipath fading channels. Share this article.
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